| Biodegradation has been accepted as the attractive and versatile method of crude oil elimination in the environment. The process is however slow in natural conditions. Therefore, the study was designed to enhance crude oil biodegradation in the soil ecosystem, and to ascertain the effect of oil pollution on bacterial population and physicochemical properties of the soil. A total of one hundred and fifty bacteria were isolated from oil free soil, and fifty-seven percent utilized crude oil at various rales as sole source of carbon and energy. Eighty-five percent of the twenty bacterial isolates from waste oil contaminated soil similarly utilized the crude oil. The crude oil degraders included species of Alcaligenes, Acinetobacter, Bacillus, Pseudomonas, Serratia, Flavobacterium, and Arthrobacter. Bacillus sp caused the highest degradation (decrease in weight) of 53% of lagoma light crude oil used in the study after 16 days of incubation at 28°C (±2). The bacterial isolates from waste oil contaminated soil exhibited higher crude oil degradation capabilities than those from oil free soil. However, crude oil utilization is not a monopoly of petroleum hydrocarbon contaminated sites. Two of the bacterial isolates from waste oil contaminated soil that could not utilize lagoma light crude oil were able to use diesel fuel and gasoline as sole source of carbon and energy. When the effect of nitrogen and phosphorous sources on diesel degradation by the isolates that could not degrade crude oil was tested, the isolate MD205W exhibited highest level (58%) of degradation capability of the diesel oil supplemented with 4mg/L of nitrogen and 2mg/L of phosphorous, while, for MD202W, highest level (46.1%) was observed with 2mg/L phosphorous and 3mg/L nitrogen. Higher rates of degradation were observed with organic rather than inorganic sources of nitrogen. The culture mediumcontaining urea, a physiologically neutral nitrogen .source, caused about 41% total weight loss of diesel fuel by MD205W. The same isolate caused a weight loss of 19% of diesel with (NH4)2SO4.Crude oil contamination of soil altered the pH of the soil. The soil moisture throughout the experimental period of 6 months was seriously affected by crude oil addition into the soil. The oil concentrations (10, 20, 30 and 40% v/w) used in the study was found to have caused increases in total nitrogen and organic carbon of the soil. Available phosphorous in the soil during the experimental period was drastically affected by soils treated with 10 and 20%' (v/w) crude oil than 30 and 40%> treatments. Higher number of total aerobic helerolrophs (x 10s CFU g"1) and crude oil utilizing bacteria (x 106 CFU g"1) were observed in oil treated soil. Though, rainy months favored total aerobic helerolrophs than dry months, it was the opposite with crude oil utilizers.The rate of oil biodegradation was enhanced by the amendment of oil polluted soil with pig dung and chicken dropping. The amendment rose pH (between 6.2 and 7.4) after 16 days of incubation at 28°C (±2), a condition that favored microbial degradation of oil in the soil. The pig dung had lotal aerobic heterolrophs of 1.8 x 10s CFU g'and 1.7 x 10° CFU g1 of crude oil degradcrs. Whilst, chicken dropping harbored 1.1 x 10s CFU g"' total aerobic heterotrophs and 1.4 x I06 CFU g1 crude oil degrading bacteria. The following genera of bacteria were identified in the samples: Micrococcus, Enterobucler, Staphylococcus, Bacillus, Pseudomonas, Escherichia, Klebsiella and Proteus were able to utilize crude oil as source of carbon and energy when tested. Gas chromatographic analysis revealed that almost all the fractions of the crude oil were attacked by the microbial consortium in chicken dropping. They may therefore be used in mitigating oil spills in the environment.Ultraviolet radiation mutagenesis was used to increase biosurfactant production by the bacterial isolate WD91A. Hemolytic activity was shown to be a measure biosurfactant quantity. The hemolylic activity of the mutant strain was found to be more than two limes greater when compared to the parent strain.
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